Most household appliances use a temperature protection device, which terminates current flow to the circuit when the ambient temperature exceeds a prescribed temperature, thereby securing the safety of the equipment. Enclosed fuses, link fuses, or plug fuses and the like, which are relatively inexpensive, are examples of this type of temperature protection device. However, these generally have low current ratings (around 2 A (amperes)) and cannot be used on household appliances, such as a microwave oven, where the circuit current used is relatively high (around 15-20 A). In such a type of household appliance, a breaker using a bimetal is sometimes used as a substitute for a temperature protection device.
However, this bimetal type breaker has a large number of components and a complex structure; it is extremely expensive compared with the various fuses described above and is one of the causes of increase in the manufacturing cost of household appliances.